Senior Java Developer - Spring / REST API / OOP

NTT DATA is looking for a freelance Senior Java Developer for a public agency based in Brussels.

• Start date: end of June 2026 (preferred)
• Duration: 31/12/2026
• Location: Brussels
• Hybrid working model with onsite presence required at least 2 days per week
• Contract type: freelance
• Deadline: 26/5/2026

We are looking for an experienced Senior Java Developer to lead the design, development, and maintenance of backend services and RESTful APIs for enterprise-level applications. This role requires strong technical expertise, a collaborative mindset, and a commitment to delivering scalable, high-quality solutions.

Key Responsibilities

• Design, develop, and maintain backend services and REST APIs using Java and Spring Boot
• Ensure code quality through unit, integration, and performance testing
• Conduct code reviews, promote development best practices, and mentor junior developers
• Collaborate with architects, business analysts, and DevOps engineers to define and deliver technical solutions
• Support deployment activities, including release management and post-go-live stabilization
• Troubleshoot and resolve production issues to ensure application performance and reliability
• Maintain and update technical documentation for services, configurations, and interfaces
• Contribute to technical design discussions, ensuring alignment with architecture and cloud strategies

Required Experience and Skills

• Minimum 10 years of experience in Java development
• Strong experience with microservices architecture (at least 5 years)
• Proven hands-on experience with the Spring framework (minimum 5 years)
• Experience integrating with SaaS solutions
• Solid understanding of REST API design, security, and best practices
• Proficiency in core Java concepts including OOP, collections, streams, and exception handling
• Experience with frameworks and tools such as Spring Boot, JPA/Hibernate, Maven or Gradle, and testing frameworks
• Strong English communication skills (C1 level or equivalent)

NTT DATA - a part of NTT Group - is a trusted global innovator of IT and business services headquartered in Tokyo. We help clients transform through consulting, industry solutions, business process services, IT modernization and managed services. NTT DATA enables clients, as well as society, to move confidently into the digital future. We are committed to our clients' long-term success and combine global reach with local client attention to serve them in over 50 countries. Visit us at nttdata.com